Lens for Improved Color Mixing and Beam Control of an LED Light Source

ABSTRACT

A multi-color LED illumination device and specifically a lens comprising a cylindrical opening extending into the lens from a light entry region at which one or more LEDs are configured. A concave spherical surface extends across the entirety of the light exit region of the lens, and a TIR outer surface shaped as a CPC extends between the light entry region and the light exit region. There are various diffusion surfaces placed on the sidewall surface of the cylindrical opening, as well as its upper planar surface and, depending on whether glare control is not needed, the exit surface of the lens. Lunes can also be configured on the sidewall surfaces of the cylindrical opening and if lessening glare is needed, also on the TIR outer reflective surface. The combination of lunes, diffusion elements, and the overall configuration of the lens provides improved color mixing and output brightness according to one embodiment. According to another embodiment, diffusion elements are manufactured and possibly increased on only select surfaces but not on the light exit region in order to lessen glare. Three light interactions in a first portion of light and two interactions in a second portion of light can improve color mixing and beam control. Those interactions includes two refractions either with an intermediate reflection or not, all of which are necessary to achieve the improved performance of the multi-color LED illumination device and lens hereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/498,671, filed Apr. 27, 2017, which is a continuation-in-part of U.S.patent application Ser. No. 15/000,469, which was filed Jan. 19, 2016.This application is also a continuation-in-part of U.S. patentapplication Ser. No. 15/000,469. Each of the above are incorporated byreference herein in their entireties.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to a light emitting diode (LED) illuminationdevice, and more particularly to a total internal reflection (TIR) lenswith an outer compound parabolic concentrator (CPC) surface to moreefficiently mix LED output in a relatively small parabolic aluminumreflector (PAR) configuration and, according to another embodiment, canlessen glare output while maintaining sufficient color mixing and beamcontrol.

2. Description of the Relevant Art

In the field of optics, and specifically non-imaging optics, there aregenerally two types of optic devices that transfer light radiationbetween a source and a target. A first type of optic device isoftentimes referred to as an illuminator; the second type of opticdevice is generally referred to as a concentrator. In an illuminator,the target is generally outside the illumination device to illuminate anobject using a variety of light sources generally inside theillumination device. A popular light source can be a solid state lightsource, such as a light emitting diode (LED). Conversely, a concentratoris generally used to concentrate a light source outside of theconcentrator onto a target inside the concentrator. A popular form ofconcentrator is a solar concentrator, used to concentrate solar energyfor photovoltaics.

Two popular forms of a concentrator are either a compound ellipticalconcentrator (CEC) or a compound parabolic concentrator (CPC). Eitherform concentrates energy from typically an infinite distance away ontoreflective surfaces of the CEC or CPC, and then to a focal point nearthe base of the CEC or CPC. Generally, a CPC is beneficial over mostother types of concentrators, including the CEC or the generalizedparabolic concentrator, in that a CPC can accept a greater amount oflight and need not accept rays of light that are solely perpendicular tothe entrance aperture of the concentrator.

FIGS. 1-3 illustrate differences between a CPC and a parabolicconcentrator in general, as well as the operation of a CPC in receivingrays of light over a fairly large acceptance angle φ. Referring to FIG.1, CPC 10 is formed from two parabolic mirrors. One arm 12 of CPC 10 isformed by cutting a parabola at point 16 and discarding the portion ofthe parabola shown in dashed line. The other arm 14 of CPC 10 is formedby cutting the parabola at point 18 and discarding the portion of theparabola shown in dashed line. The arms 12 and 14 are formed equaldistance from central axis 20, and rotated about central axis 20 to formthe symmetrical CPC reflective surface.

Turning to FIG. 2, shown in cross section is a general parabolicconcentrator 26 with reflective surface 22 rotated about central axis24. Comparing FIGS. 1-2, the entrance aperture of parabolic concentrator26 is much larger than that of CPC 10. However, as shown in FIG. 3, CPC10 can receive light 28 at an acceptance angle φ dissimilar from lightthat is perpendicular to the entrance aperture. Accordingly, CPC 10accepts a greater amount of light than other forms of concentrators,such as the parabolic concentrator.

Contrary to concentrators, illuminators send light outward as opposed toreceiving light inward. Illuminators typically have a light sourceplaced near the base of a secondary optical element. The light sourceforms a primary optical element in that it generates light, examples ofwhich include incandescent lights or solid state lights, such as lightemitting diodes (LEDs). LEDs are solid state devices that convertelectrical energy to light, and generally comprise one or more activeregions of semiconductor material interposed between oppositely dopedsemiconductor layers. Light is emitted from the active region andsurfaces of the LED.

In order to generate a desired output color, it is sometimes necessaryto mix colors of light using what is known as multi-color LED lights.Multi-color LED light can include one or more LEDs, which are mounted ona substrate and covered by a hemispherical silicon dome in aconventional package. The LEDs can emit blue, red, green, or othercolors, and a combination of such can be mixed to produce any desiredcolor spectrum.

Because of the physical arrangement of the various LED sources, shadowswith color separation and poor color uniformity can exist at the output.For example, a source featuring blue and yellow may appear to have ablue tint when viewed head on, and a yellow tint when viewed from theside. Thus, one challenge associated with multi-color light LEDs ishaving good spatial and angular separation, otherwise known as spatialand angular uniformity projected outward in the near and far field ofthe LED source.

One method used to improve spatial and angular uniformity, and thuscolor mixing, is to reflect or refract light off several surfaces beforeit is emitted. Color mixing can also be achieved using a combination ofreflection and refraction. Both have the effect of disassociating theemitted light from its initial emission angle. Uniformity typicallyimproves, but each light interaction (reflection and refraction) has anassociated loss.

FIG. 4 illustrates secondary optical elements used in conjunction withthe primary optical element (LED source). The secondary optical elementsof FIG. 4 solely reflect light using either lens 30 or reflectivehousing 32. Both the reflective housing 32 and lens 30 are usedprimarily to collimate the light output, as shown by the collimatedoutput of rays 40 and 42. The LEDs, e.g., red, green, blue, and white,can be spaced from each other along a base plane to form array 34further shown in FIG. 5. The array of LEDs extends in planar fashionalong a base plane with cover 36 covering the planar arrangement ofLEDs. Cover 36 may be mounted to the base, which is preferably a printedcircuit board with a heat sink. LED array 34 is centered andperpendicular to central axis 38, which is preferably the central axisfor reflector housing 32 and lens 30 being symmetrical about axis 38.

As shown in FIG. 4, lens 30 is a transparent lens made of plastic orglass, having a refractive index greater than air. As light beam 40enters lens 30, it enters at a right angle to the convex sphericalsurface and reflects from the outer surface in collimated fashionoutside of the lens. Thus, lens 30 is typically known as a total innerreflection (TIR) lens, with the angular outside surfaces made of areflective material in the shape of a parabola rotated around centralaxis 38. The reflective portion is mathematically described as aparabola f(y)=ay²+by+c, where y is the height of the lens from an entryto an exit.

Rays which do not enter the concave entry of lens 30 can be reflectedfrom housing 32, such as ray 42. In either instance, FIG. 4 illustratesone example of total internal reflection using two reflective surfaces,one on the external surface of lens 30 and the other on the externalsurface of housing 32. In either instance, only a single lightinteraction occurs, that being a reflection rather than refraction.Thus, no matter where LEDs 41 appear within, for example, a matrix withdifferent colors of LEDs spatially positioned across the matrix, theoutput of the secondary optical element is collimated using a singlelight interaction.

Turning now to FIG. 6, lens 44 is shown. Lens 44 does not require areflective housing or an air gap between a reflective housing and a TIRlens. Lens 44 is placed in close proximity to the LED array 34 so as tocapture all light emitted from the LEDs, without need of a reflectivehousing. Lens 44 includes a spherical, concave entry surface 46 and aspherical, convex exit surface 48. In addition, exit portion 50 can bemade neither convex nor concave. The term convex is used to describe thespherical portions with convex being relative to the lens inner regionand extending inward toward a center of the lens, while concave extendsoutward from the lens inner portion. Both the inward and outwardextensions occur symmetrically about a central axis.

As shown in FIG. 6, any rays which extend from LED array 34 are eitherreflected 52 or refracted 54. Ray 52 reflects from the TIR outer surfaceof lens 44, whereas ray 54 refracts from convex surface 48. According tothe law of refraction, n_(p) sine φ_(p)=n_(a) sine φ_(a). For example,using this equation and knowing that the index of refraction for air,n_(a), is less than the index of refraction for plastic, n_(p), thenφ_(p)<φ_(a). This angular relationship is described in the angles φ_(p)and φ_(a) shown in FIG. 6 to indicate the refraction and the change inangle from the perpendicular as ray 54 extends from, for example,plastic lens to air. In either case in which ray 52 is reflected or ray54 is refracted, only one light interaction is needed for lens 44.Moreover, only one light interaction is needed to form a collimatedoutput; thus, a collimation lens. It is noted that concave surface 46 isarranged so that whatever rays emit from LED array 34, those rays enterthe concave surface 46 at substantially right angles; thus, norefraction takes place on the light entry region.

FIG. 7 illustrates lens 60 having a TIR surface symmetrical around acentral axis. However, instead of the light entry region being concave,the light entry region 62 of lens 60 is convex. Moreover, there arestraight sidewall surfaces 64 of equal distance from the central axis,extending from the planar base on which LED array 34 is attached toconvex surface 62. Thus, rays 66 are refracted on convex surface 62,whereas rays 68 are refracted on the sidewall surface 64 and thenreflected on the TIR surface. No more than one refraction occurs ineither instance.

In addition to convex light entry surface 62, light exit surface 70 canalso be convex as shown in dashed lines. Unfortunately, using a convexentry and exit surfaces causes light rays 72 to undergo two refractions,one on the entry and another on the exit. The second refraction at theexit may retain collimation, however, angular uniformity becomes aproblem as the output projects at intensity peaks that are spaced fromone another, and not evenly mixed across a plane perpendicular to thecentral axis. Moreover, two light interactions, both of which arerefractive, significantly impacts on the output color spectrum as wellas the output brightness itself. It is typically important to avoidrefraction, since refraction can change the propagation path of theemitted light depending on the light wavelength. For example, arefracted beam that is blue at the source can take on a differentpropagation path through the lens than a light beam that is green. Thus,in settings that utilize, for example, red, green, blue, and white LEDsources, it is generally desirable to avoid refraction, since refractionis typically wavelength dependent. It is also advantageous to avoidnumerous light interactions, including both refraction and reflection.The more light interactions that occur, the output lumen brightness candeleteriously be affected.

In each of the lens structures described hereinabove, collimation isachieved at the projected output. However, pure collimation containscertain drawbacks. For example, the collimated output using two lightinteractions at shown in FIG. 7 has an inherent color mixing drawback.The output, while having intensity peaks, also has relatively poorangular uniformity. Each LED within the module 34 produces an outputthat extends outward in a radial angle approximately 180 degrees. Forexample, a red LED can be spaced from a green LED, and the output ofeach project their angular output a spaced distance from one anotheronto the two-light interactive lens which then, through refractionand/or reflection, collimates and projects the non-uniform angularoutput. The poor angular uniformity of the output will, unfortunately,negatively impact on color mixing. If improved color mixing is desired,pure collimation should not be the primary reason for selecting a lens.Moreover, color mixing can oftentimes reduce the output intensity andtherefore having more than two light interactions is problematic if lowpower LED applications are all that are possible.

It would be desirable to achieve an improved lens design that hasimproved color mixing while selectively using a modified collimatedoutput from certain portions of the lens design. Such a lens may requiremore than two light interactions to achieve not only better angularuniformity, and thus color mixing, but also can be implemented if theLED output can be appropriately increased. By using an increased LEDoutput with at least three light interactions, it is further desirableto collimate the outer radial regions of the lens output while avoidingcollimation on the inner radial regions of the lens output. Selectivelytailoring collimation to the outer region affords more control throughappropriately placed diffusion lunes that diffuse the rays collimatedfrom the outer region to not only improve angular uniformity notavailable in conventional lens designs but also to maintain improvedcolor mixing across the entire output surface of the lens consistentwith what is achieved in the inner radial region.

Improved color mixing across the entire output surface is achieved notthrough collimation lenses as shown in FIGS. 4, 6 and 7, or derivativesthereof, since such lenses do not selectively control the lens output atthe outer radial region, nor do they remove the concave or convex entryor exit surfaces at the inner radial region that cause poor angularuniformity, and thus poor color mixing of an LED output.

SUMMARY OF THE INVENTION

The problems outlined above are in large part solved by an improved lenshaving a straight entry at the inner radial region to improve colormixing of LED output near a central axis and at the detriment ofcollimation from that inner radial region. The improved lens also has astraight sidewall entry at the outer radial region to improve colormixing of LED output farther from the central axis even though such LEDoutput is collimated. The straight sidewall entry is, however,configured with a surface that diffuses or scatters the light from theLED as it impinges upon a CPC reflective output surface and then to aconcave spherical exit bounded by the CPC reflective outer surface. Byconfiguring the non-collimated light exiting the inner radial region andthe collimated, yet diffusion treated, light exiting the outer radialregion, the outer radially emitted light surrounds the inner radiallyemitted light to make the projected light appear in the near and farfield to be better color mixed across a broader angular range of the LEDoutput. The lens, used as a secondary optical element, thereforeachieves an improved methodology for transferring color mixed light fromone or more LEDs.

According to a first embodiment, a lens is provided for receiving lightfrom an LED. The lens includes a cylindrical opening extending into thelens from a light entry region. The cylindrical opening is configured toreceive the entirety of light from the LED. Across the entirety of alight exit region is a concave spherical surface. The concave sphericalsurface extends inward towards a central axis and is symmetric aboutthat central axis. The arcuate path of the concave spherical surfaceextends to the entire outer surface near the light exit region. Theouter surface is a TIR outer surface shaped as a CPC, which extendsbetween the light entry region and the light exit region.

The cylindrical opening comprises a sidewall surface facing toward andequal distance from a central axis. The sidewall surface receives lightat the outer radial region, where light exits the LEDs more than, forexample, 20 degrees from a central axis and which do not strike thestraight, upper substantially circular plane that is perpendicular tothe sidewall surface and forms the upper region of the cylindricalopening. Any light that strikes the upper substantially circular planeis referred to as the light at the inner radial region.

The sidewall surface preferably comprises a plurality of lunes, each ofwhich is substantially planar having a length and width, the lengthbeing greater than the width and extending parallel to the central axis.The lunes are spaced equal distance from the central axis and terminateon the upper region of the cylindrical opening. Depending on the numberof lunes, the upper plane becomes more circular as the number of lunesincreases. The number of lunes is preferably between 8 and 20. If morethan 20 lunes are used, for a given lens dimension, more collimation canoccur for radially extending LED light output, which is deleterious tothe desired color mixing in the inner radial region of the lens. Lessthan 8 lunes would form more of a square upper plane causing a greaterbeam intensity loss than what can be achieved by simply increasing theLED output.

The lens comprises a unibody construction and is of the same materialcontiguous throughout, with no seams, adjointments, or abutments of onebody to another within the entirety of the lens, so that the lens isseamless and preferably made from, for example, a molding apparatus. Theunibody material preferably has a refractive index greater than air, andis configured between surfaces formed by the sidewalls of thecylindrical opening, the concave spherical surface extending across theentirety of the light exit region, and the TIR outer surface shaped as aCPC.

According to another embodiment, an illumination device is provided. Theillumination device comprises a unibody lens having a reflective outersurface shaped as a CPC around a central axis between an entry surfaceand a spherical concave exit surface. A plurality of LEDs are configuredproximate to the entry surface and spaced from each other along a baseplane perpendicular to the central axis. A plurality of lunes extendsperpendicular from the base plane, each of the lunes having an elongatedplanar surface, wherein the elongated planar surface is configured anequal distance along the central axis to an upper plane that is parallelto the base plane. The upper plan extends radially outward from thecentral axis to a distal radius. Each of the plurality of lunesterminates at a 90° angle on the distal radius to form a cylindricalsurface bound by the plurality of lunes, and the upper plane facinginward toward the base plane and the LEDs.

The filling material of the unibody lens can be plastic or glass, forexample. Such filling material can be injection molded acrylic,polymethylmethacrylate (PMMA), or any other form of transparentmaterial. The reflective surface of the outer TIR surface shaped as aCPC comprises any surface which reflects the light rays coming from theinternal fill material, such as a square plate polyhedral reflectivesurface.

According to all embodiments, the lens hereof purposely avoids using anyhousing reflector, but is implemented in a PAR form factor that providesuniform color throughout the standard 0°, 25°, and upwards to 40° beamangles. The lens preferably has a pipe from the entry portion to theexit portion of no more than 1.4 inches, with the spherical concave exitsurface extending to the TIR reflector surfaces being no more than 2.5inches. The bottom diameter of the lens at the base plane is no morethan 1 inch. Accordingly, the present lens is compact; thus,illustrating one benefit of using a CPC dimension rather than a standardparabolic dimension. The relatively small form factor that utilizes acompact design implemented through a CPC configuration achieves not onlysuperior color mixing with improved, if not superior, brightnesscontrol, but does so using the unique lens configuration on both theentry and exit surfaces, and further being able to adjust the drivecurrent supplied to the LED loads to accommodate any changes inwavelength-dependent refraction.

A methodology is provided to achieve these beneficial results oftransferring light from an LED. The method includes transmitting a firstportion of the light through air at a plurality of first angles relativeto a central axis around which the lens is formed. Accordingly, thefirst portion of light, as well as a second portion of light,transmitted from the light source is typically Lanbertian, which meansthat the LED matrix or array of spaced LEDs emits light in alldirections. However, the TIR secondary optical element extracts andcollimates the light at the light exit surface. The method furthercomprises first refracting the first portion at a sidewall surface ofthe light entry surface. The refracted first portion of light is thenreflected from an outer surface of the lens back into the lens, where asecond refracting takes place. The second refracting refracts thereflected first portion from a spherical concave surface into the air.

According to a further embodiment, the method comprises transmitting asecond portion of light through air at a plurality of second anglesrelative to the central axis less than the plurality of first angles. Athird refraction occurs whereby the second portion is again refracted ata planar surface perpendicular to the central axis into the lens. Afourth refraction occurs whereby the third refracted second portion isagain refracted from the spherical concave surface into the air.

According to an alternative embodiment, a lens within an illuminationdevice is provided that can achieve lessened glare output whilemaintaining adequate color mixing and beam control through the secondaryoptical element, or lens. The alternative lens configuration is one thatimplements a tapered cylindrical opening, rather than a cylindricalopening having a straight sidewall. The tapered sidewall of the lensinner radial region is proximate the light entry region, and can includea diffusion treated surface upon a first plurality of lunes to maintainsufficient beam control. The diffusion treated first plurality of lunesalso provides appropriate color mixing.

Importantly, the concave spherical surface of the light exit region doesnot have any diffusion treatment on that surface. By avoiding anydiffusion treatment, or any manufactured diffusion surface, the concavespherical surface of the light exit region is left clear and relativelysmooth as a lens is taken from a smooth injection mold device surface.An exit surface that is not diffusion treated, or diffusion manufacturedthrough texturing via etching, sandblasting, or by configuring amicro-lens array on the surface, the exit surface therefore beneficiallyreduces any glare output from the illumination device and through thelens. Eliminating any diffusion treatment, manufactured diffusion, ortexturing on the entire concave spherical surface of the light exitregion, various forms of direct and indirect glare are minimized.

Instead of placing diffusion treatment on the light exit region of theconcave spherical surface, diffusion treatment or manufactured diffusionis placed on a surface of the lens entirely on the light entry region,and specifically on the tapered sidewall surface and the upper planarsurface of the tapered cylindrical opening. By placing the diffusion atthe light entry region and not at the light exit region, glare isminimized yet color mixing and beam control are maintained.

According to the alternative embodiment, the lens includes a taperedcylindrical opening having a tapered sidewall surface extending into thelens from a light entry region configured for receiving the entirety oflight from one or more LEDs. The lens further includes a concavespherical surface extending across the entirety of the light exit regionof the lens. Unlike the light entry region having the tapered sidewallsurface and the upper planar surface that are diffusion treated ordiffusion manufactured, the entirety of the concave spherical surface isneither diffusion treated, diffusion manufactured, or textured in anyway. The lens further includes a TIR outer surface shaped as a CPCextending between the light entry region and the light exit region.

The tapered cylindrical opening extends partially into the lens from thelight entry region and is centered along a central axis of the lens. Inorder to take on its tapered shape, the tapered sidewall surface isconfigured about the central axis a decreasing radial distance from thecentral axis from the light entry region toward the light exit region.To form the taper, the decreasing radial distance is approximately4°-10° relative to the central axis.

According to yet a further embodiment of the alternative embodiment, thetapered sidewall surface includes a plurality of planar lunes extendingradially inward toward the central axis from the opening to the upperplane, with a manufactured or diffusion treated surface on each of theplurality of lunes. The plurality of planar lunes along the taperedsidewall surface are referred to as a first plurality of lunes. A secondplurality of lunes exists on the TIR outer surface and are used tointernally reflect any light entering the lens back out to the lightexit region, and specifically the concave spherical surface of the lens.The second plurality of lunes assist in color mixing while collimatingthe light exiting the light exit region. The second plurality of lunesextends from the tapered cylindrical opening to the concave sphericalsurface at the light exit region, whereby the second plurality of lunesoutnumber the first plurality of lunes by a ratio of between 1.5:1 to2.5:1.

Further to the alternative embodiment, an illumination device isprovided. The illumination device comprises a unibody lens having areflective outer surface shaped as a CPC around a central axis between adiffusion manufactured light entry surface and a non-diffusionmanufactured spherical concave light exit surface. The illuminationdevice of the alternative embodiment further comprises at least one LED,or a plurality of LEDs, proximate to the light entry surface and spacedfrom each other along a base plane perpendicular to the central axis.The illumination device according to the alternative embodiment stillfurther comprises a first plurality of lunes upon the light entrysurface, each of the first plurality of lunes having an elongated planarsurface extending a decreasing distance from the central axis from thebase plane to an upper plane that is parallel to the base plane. Asecond plurality of lunes are configured on the reflective outer surfaceof a TIR lens shaped as a CPC, each having a second elongated planarsurface extending an increasing distance from the central axis from thebase plane to the spherical concave surface of the light exit region.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to theaccompanying drawings.

FIG. 1 is a plan view of a compound parabolic shape relative to aparabolic shape;

FIG. 2 is a plan view of a parabolic shape having a wider radius from acentral axis than the compound parabolic shape;

FIG. 3 is a plan view of a compound parabolic concentrator typicallyused to accept and concentrate solar rays onto a focal point;

FIG. 4 is a side cross sectional view of a lens mounted within areflective housing to achieve total internal reflection;

FIG. 5 is a view along plane 5 of FIG. 4 showing an array of LEDs;

FIG. 6 is a side cross sectional view of a TIR lens absent a reflectivehousing to achieve total internal reflection using only one lightinteraction;

FIG. 7 is a side cross sectional view of a TIR lens absent a reflectivehousing to achieve total internal reflecting using no more than twolight interactions;

FIG. 8A is a side cross sectional view a lens with a TIR outer surfaceshaped as a CPC and having up to three light interactions to achieveimproved output collimation and color mixing according to one embodimentof the present invention;

FIG. 8B is a blow up cross sectional view of the diffusion surfaces;

FIG. 9A is a view along plane 9 of FIG. 9 showing a cylindrical openinghaving a plurality of lunes arranged along the sidewall surface of thecylindrical opening;

FIG. 9B is a blow up cross sectional view of the two lunes of a TIR lensshaped with a CPC;

FIG. 10A is a side cross sectional view of the lens of FIG. 8A accordingto an alternative embodiment in which the concave light exit region doesnot comprise a diffusion surface and the light entry region comprisesdiffusion surfaces and a tapered sidewall surface to minimize glare;

FIG. 10B is a blow up cross sectional view of the diffusion surfacesconfigured on the light entry region of the lens according to theembodiment of FIG. 10A; and

FIG. 11 is a cross-section view along plane 11 of FIG. 10A showing thereflective TIR outer surface of the lens having a plurality of lunes,each having a width that extends around the circumference of the outersurface and a length extending from the light entry region to the lightexit region.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 8A illustrates lens 80 filled with material 82, e.g., an injectionmolded light transparent material. Material 82 is bound between lightentry region 84, light exit region 86, and TIR outer surface 88, whichis shaped as a CPC. TIR outer surface 88 has a smaller exit region thena parabolic TIR, shown in dashed line 90. Moreover, exit region 86comprises concave spherical surface 94, instead of most conventionalparabolic lenses having a flat surface, shown in dashed line 96. Thus,FIG. 8A illustrates a comparison between a conventional parabolic lens91 and the present lens 80. Present lens 80 is not only shaped as a CPC,but also is more compact in its configuration, being less than 2.5inches in diameter for exit region 86, 1 inch in diameter for entryregion 84, and no more than 1.4 inches in height from the entry regionto the exit region. The entry region is defined as a planar base onwhich the LEDs 100 reside. The overall maximum height of the compact PARdimension of the present invention is 1.4 inches from the planar base tothe outer extents of the TIR reflective surface 88 at which it joins theconcave spherical surface 94.

Of import, the compact PAR configuration of lens 80, which is shaped asa CPC, is beneficial over the conventional parabolic lens. Conventionallens 91 can receive light passing through a sidewall surface 102 nearthe light entry region 84, such sidewall surface constitutes thesidewall surface of a cylindrical opening, also having an upper planarsurface 104. The dashed line indicates refraction at angles φ_(PA1) andφ_(PM2) at the plastic-to-air interface of the parabolic lens. Next, areflection occurs at the TIR external surface of lens 91, shown atangles φ_(R3) and φ_(R4), whereby the reflected light is then refractedat the exit surface of lens 91 by the interaction of φ_(PM2) to φ_(PA2).The resulting exiting light ray or beam may not be collimated. Thus, itis desirable to form a collimated lens, which can be achieved by strictadherence to the configuration of lens 80, with a cylindrical openingthat forms sidewall surface 102 and upper planar surface 104, along withconcave spherical surface 94, where surface 94 must extend across theentirety of the light exit region from the central axis about which lens80 is symmetrical to external surface 88.

FIG. 8A illustrates that any beam that strikes sidewall surface 102 mustgo through three light interactions. For example, beam 106 goes througha refraction φ_(A1)/φ_(M1) at sidewall surface 102 to a reflectionφ_(R1)/φ_(R2), to another refraction φ_(M2)/φ_(A2) on surface 94. Beam108 also goes through three interactions. The first interaction is arefraction, followed by a reflection, ending with another refraction.Thus, every beam that enters the sidewall surface near the beam entryportion goes through the sequence of refraction, reflection, andrefraction, finally exiting the light exit region as a collimated lightbeam, which is not achievable in conventional lens 91. For brevity andclarity of the drawings in showing the various ray paths, which canexceed several hundred if not thousands, only two are shown for lens 80entering the sidewall surfaces. Moreover, so as not to obscure the raypath line, material 82 is not shown in cross-hatch; however, it isunderstood that in the region between the cylindrical opening near thelight entry region to the concave spherical surface of the light exitregion, lens 80 is filled with unibody material 82, which is contiguousand non-interrupted, such as injection molding.

In addition to transmitting a first portion of light from LEDs 100through air attributable to the cylindrical opening where it impingesupon sidewall surface 102, a second portion of light can be sent throughair of the cylindrical opening where it impinges upon planar uppersurface 104. The first portion of light is first refracted at surface102, then reflected at surface 88, then second refracted at surface 94.The second portion of light 110 is third refracted φ_(A3)/φ_(M3), if itimpinges upon the planar upper surface at a non-perpendicular angle,where it is later fourth refracted φ_(M4)/φ_(A4) on surface 94.

The first portion of light from the outer radial region of the LEDoutput is shown collimated as it exists as beam 106. The first portion,however, passes through diffusion surfaces on the sidewall surface 102to scatter, or mix the light output to achieve both angular and linearuniformity of the output. Such diffused, collimated output is purposelyplaced on the outer radial region to surround the non-collimated innerradial region of the LED output to achieve color mixing at the near andfar field. The improved color mixing is due to the unique configurationof the cylindrical opening of the light entry region to the concavespherical surface of the light exit region, bound by a reflective outersurface being CPC-shaped to achieve an overall compact dimension of aPAR lamp.

On sidewall surface 102, planar upper surface 104, and exit surface 94of lens 80 is a diffuser surface 112, shown in FIG. 8B. Diffuser surface112 scatters light from the various LED sources, resulting in a widerbeam angle. In general, diffuser surface 112 is preferably configuredwith some combination of differently textured surfaces and/or patterns114, so that light 116 entering the surface will get scattered ordiffused, shown by light 118. For example, lensets that perform thescattering can be rectangular or square shaped domes, and may be smallenough so that the curvature of the lensets is defined by the radius ofthe arcs that create the lensets.

FIG. 9A illustrates a plurality of lunes 120, when viewed from the baseof lens 80 along plane 9-9 of FIG. 8A. Peering into the cylindricalopening, a series of substantially flat or planar lunes 120 extend alongsidewall surface 102 spaced equal distance from central axis 122. Shownare eight lunes, and preferably, the improved lens design hereof usesbetween eight to no more than 20 lunes to enhance color mixing in theinner cylindrical opening into which the LED output enters. Each lunehas an elongated surface that extends the entire length of the sidewallsurface from the planar base on which LEDs 100 reside to upper planarsurface 104. The elongated surface of lunes 120 extend perpendicularfrom the base plane, spaced equal distance along central axis 122 toupper plane 104 that is parallel to the base plane. The lunes are simplyplanar cutouts from lens 80, formed as part of the injection moldingprocess when the fill material is applied to the mold, with the moldouter regions within the cylindrical opening of the lens having aplurality of circumferentially configured planar surfaces.

FIG. 9B is an expanded view of a region showing two lunes 120 a/120 b,and provides a general description as to why such surfaces are definedas lunes. The lune surfaces are formed as a concave-convex area, shownin cross hatch, bounded by two circular arcs. The lune surfaces 120a/120 b are formed therefrom.

Turning now to FIGS. 10A, 10B and 11, an alternative embodiment for alens is shown. Contrary to the lens shown in FIGS. 8A and 8B, the lensin FIGS. 10A and 10B is a lens that emits a lower glare from the lightexit region 86, and specifically the concave spherical surface 94 thatextends across the entirety of the light exit region 86. Since lens 80shown in FIG. 10A is one having a TIR outer surface and shaped as a CPC,many like numerical identifiers exist between FIG. 10A and FIG. 8Adescribing a TIR lens 80, albeit some of the surfaces of lens 80 in FIG.10A are different from the surfaces of lens 80 in FIG. 8A.

For example, the concave spherical surface 94 of the light exit region86 in the alternative embodiment shown in FIG. 10A does not have anydiffusion treatment or any diffusion manufactured thereon. Accordingly,FIG. 10B shows a diffusion surface of textured patterns 114 so thatlight 116 entering the surface will get scattered or diffused, shown bylight 118. Importantly, diffuser surface 112 exists only on the lightentry region, and specifically on the tapered sidewall surface 102 andthe upper planar surface 104. While similar numerals are shown for thesidewall surface 102 and the upper planar surface 104 of the cylindricalopening, the alternative embodiment of FIG. 10A indicates nonetheless adifference from the sidewall surface 102 and the upper planar surface104 in FIG. 8A. Specifically, the sidewall surface 102 in FIG. 10A istapered and not perpendicular to the base plane on which the LEDs 100extend, while the sidewall surface 102 in FIG. 8A is a straight sidewallsurface that is perpendicular to the base plane on which the LEDs 100extend. More diffusion or texture can be applied to the tapered sidewallsurface 102 than to the straight sidewall surface 102.

FIGS. 10A and 10B do not illustrate any diffuser surface on the lightexit region 86, and specifically the concave spherical surface 94 of thelight exit region 86. All diffusion is placed on the tapered sidewallsurface 102 and the upper planar surface 104, of the light entry region.By placing the diffuser surface only on the light entry region, andtapering the sidewall of the tapered cylindrical opening, color mixingcan be maintained somewhat close to that of the embodiment shown in FIG.8A. However, by removing any diffuser surface from the light exitregion, a lower glare can be achieved.

It is typically recognized that there are at least two types of glare:direct or indirect. Direct glare is the glare that appears when a personlooks straight onto the illumination device source, or the LED behindthe secondary optic lens. Indirect glare is that which occurs fromillumination output reflected off surfaces in the field of view. Thosesurfaces can be within the lens itself or outside the lens, such as onan object distal from the illumination device (e.g., a desk, computerscreen, etc).

Regardless of the type of glare, glare in general can cause significantproblems such as blurred images, eye strain, or even headaches. Typicalways in which to deal with glare and the visual discomforts associatedtherewith, are anti-glare structures. Popular anti-glare structuresinclude diffusive films and reflective screens. Anti-glare structuresare oftentimes placed on the illumination device in an attempt to matchand offset any reflection that might arise from the illumination output.It is difficult at best to perform such matching and, if donesuccessfully results in a complicated design and manufacturing of thematching and offsetting screens that almost certainly results in poorlight efficiency output from the illumination device.

The problems of glare and any failed attempts to offset that glare byanti-glare reflective filtering, screening, etc. are eliminated entirelyby ensuring that no such anti-glare screening, filtering or offsettingoccurs on the light exit region. Such problems are therefore solved byremoving any diffusive surface from the concave spherical surface 94 andinstead tapering the sidewall surface 102 to effectuate diffusion closerto the light source, or LEDs 100. This allows the natural refraction andreflection within the lens to cause any necessary offset or matching tooccur within the lens and not to add any additional glare by attemptinga diffusive surface on the light exit region 86.

Minimizing glare in ceiling-mounted light fixtures, and specifically PARdownlights that use LEDs not only eliminates glare zones, but accordingto the anti-glare alternative embodiment shown in FIGS. 10A-11, nooffset, reverse compensation, glare-tuning, matching, or any otherexpensive and difficult to manufacture exit diffuser surfaces are neededon the concave spherical surface 94 of the exit region 86. All glarecontrol and glare-zone elimination occurs at the light entry region, andspecifically through use of a tapered cylindrical opening and thevarious refraction and reflections that occur within the CPC shapeitself.

As shown in FIG. 10A, LEDs 100 are moved closer to the upper planarsurface 104, as shown in dashed line, and the opening 130 of the taperedcylindrical opening can be made of a larger diameter, possibly more thanone inch so that the diameter of the concave spherical surface 94relative to the central axis 132 is between 2-2.5 times the diameter ofthe opening 130, also relative to the central axis 132. Accordingly, ifthe diameter of opening 130 is greater than one inch, and the diameterof the concave spherical surface 94 diameter is 2.5 inches, the ratiowould be less than 2.5. The amount of taper of the sidewall surface 102can be described as an angle Ø relative to the central axis 132.Accordingly, angle Ø of the tapered sidewall surface relative to thecentral axis 132 can range between 4° to 10°. The amount of taper isprimarily determined by the specific beam angle requirement. Also, theamount of diffusion manufactured on the tapered sidewall surface 102 andthe upper planar surface 104 of the light entry region is dependent uponthe amount of color mixing and beam uniformity needed.

Like the embodiment shown in FIGS. 8A-9B, the low glare embodiment shownin FIGS. 10A-11 also include a first plurality of lunes on the sidewallsurface 102. The only difference between the two different embodimentsis that the lunes on the sidewall surface 102 in FIG. 10A are taperedplanar surfaces and the first plurality of lunes on the embodiment inFIG. 8A are not tapered and extend perpendicular to the base plane.Specifically, the tapered first plurality of planar lunes extend as partof the tapered sidewall surface radially inward toward the central axisfrom the opening 130 to the upper plane 104. All of the first pluralityof lunes are of equal length and all of the first plurality of planarlunes are ones that extend from the opening to the upper plane. Each ofthe first plurality of tapered lunes has a manufactured diffusionsurface thereon.

While the TIR reflective surface in the embodiment of FIG. 8A, shown asnumeral 88 does not have a second plurality of planar lunes, theembodiment in FIGS. 10A-11 for low glare configuration does. As shown inthe cross-section 11-11 of the outer reflective surface 88 in the secondembodiment, a second plurality of planar lunes 140 are arranged upon thereflective outer surface 88. Each of the second plurality of lunes 140has a second elongated planar surface extending an increasing distancefrom the central axis 132 from the opening 130 of the base plane onwhich LEDs 100 exist to the spherical concave exit surface 94. Each ofthe second plurality of lunes are compound parabolic in shape to conformto the CPC outer surface, yet having a planar shape bent as it extendsfrom the light entry region to the light exit region. Preferably, theratio between the number of second plurality of lunes and the number offirst plurality of lunes is between 1.5:1 and 2.5:1. Thus, if the firstplurality of lunes is between 8 and 20, the second plurality of lunes isbetween 12-50. As shown in FIG. 11, the second plurality of lunes 140preferably exists on the inside surface of the outer reflective surface88. The second plurality of lunes 140, are therefore reflective planarsurfaces that reflect all light that are received on the lunes back intothe lens 80 and out through the light exit surface 86. The secondplurality of lunes therefore achieves TIR functionality, but within aCPC configuration.

It will be appreciated to those skilled in the art having the benefit ofthis disclosure that this invention is believed to provide an improvedlens configuration that achieves improved color mixing. The improvedcolor mixing occurs by treating a collimated outer radial region of theLED module output, while maintaining non-collimation on an inner radialregion of the LED output. More than three light interactions are neededto achieve the improved color mixing, with both improved spatial andangular uniformity. Improved glare control is also achieved using ataped diffusion-manufactured sidewall surface of a light entry regionwithout any diffusion manufactured on the concave spherical surface ofthe light exit region. Further modifications and alternative embodimentsof various aspects of the invention will be apparent to those skilled inthe art in view of this description. It is intended that the followingclaims be interpreted to embrace all such modifications and changes.Accordingly, the specification and drawings are to be regarded in anillustrative, rather than a restrictive, sense.

1. (canceled)
 2. An illumination device, comprising: a unibody lenshaving a reflective outer surface defining a compound parabolicconcentrator around a central axis between a light entry surface and aspherical concave light exit surface, the light entry surface defining asubstantially cylindrical sidewall surface and an upper planar surface,a lower portion of the sidewall defining a light entry region defining abase plane perpendicular to the central axis; and a plurality oflight-emitting diodes proximate the base plane and configured to radiatelight toward the light entry surface; wherein: the sidewall surfacecomprises a first diffuser surface; and the upper planar surfacecomprises a second diffuser surface.
 3. The illumination device asrecited in claim 2, wherein the first and second diffuser surfacescomprise a combination of differently textured surfaces.
 4. Theillumination device as recited in claim 2, wherein the first and seconddiffuser surfaces comprise a combination of different patterns.
 5. Theillumination device as recited in claim 2, wherein the first and seconddiffuser surfaces comprise lensets.
 6. The illumination device asrecited in claim 5, wherein the lensets comprise rectangular shapeddomes.
 7. The illumination device as recited in claim 5 wherein thelensets comprise square shaped domes.
 8. The illumination device asrecited in claim 2, wherein the spherical concave exit surface extendsaround the central axis an entire distance to the reflective outersurface.
 9. The illumination device as recited in claim 2, wherein thelens is a light transparent lens, and reflective outer surface isconfigured to reflect substantially all of the light from thelight-emitting diodes that is directed to the reflective outer surface.10. The illumination device as recited in claim 2, wherein the sphericalconcave exit surface is configured to receive all of the light from thelight-emitting diodes that is directed to and reflected from thereflective outer surface.